Infrastructure equipment and method

ABSTRACT

An infrastructure equipment for forming part of a mobile radio network includes a transmit and receive unit, to transmit and receive data to and from mobile communications devices via a wireless access interface, and a controller processing requests for communications resources from the mobile communications devices. Plural associated communications devices are arranged to form a group, and each of the associated communications devices of the group includes a same common identifier, with respect to which communications sessions can be established to communicate data via the mobile radio network, and the controller is arranged in combination with the transmit and receive unit to respond to a request from one of the communications devices of the group to establish a communications bearer using the common identifier.

FIELD OF THE INVENTION

The present invention relates to communications systems which arearranged to communicate data with mobile communications devices via awireless access interface. The present invention also relates tocommunications devices which communicate data with mobile radionetworks, infrastructure equipment for mobile radio networks and methodsfor communicating data with mobile radio networks.

BACKGROUND OF THE INVENTION

Mobile communication systems have evolved over the past ten years or sofrom the GSM System (Global System for Mobiles) to the 3G system and nowinclude packet data communications as well as circuit switchedcommunications. The third generation project partnership (3GPP) has nowbegan to develop a mobile communication system referred to as Long TermEvolution (LTE) in which a core network part has been evolved to form amore simplified architecture based on a merging of components of earliermobile radio network architectures and a radio access interface which isbased on Orthogonal Frequency Division Multiplexing (OFDM) on thedownlink and Single Carrier Frequency Division Multiple Access (SC-FDMA)on the uplink.

At present mobile communications services are dominated by human tohuman (H2H) communications, that is, data which is transmitted by ahuman to another human or at least data that is transmitted forpresentation to a human being. It is now recognised that there is adesire to cater for communications to and/or from machines which arereferred to generally as machine type communications (MTC) or machine tomachine (M2M) communications. MTC communications can be characterised ascommunicating data which has been generated from a source automatically,for example in response to some other stimulus or event reporting someattribute of the machine or some monitored parameter or so-called smartmetering. Thus whilst human communications such as voice can becharacterised as being communications requiring a communications sessionof some minutes with data being generated in bursts of severalmillisecond with pauses there between or video can be characterised asstreaming data at a substantially constant bit rate, MTC communicationscan generally be characterised as sporadically communicating smallquantities of data although it would be appreciated that there is also awide variety of possible MTC communications.

As will be appreciated it is generally desirable to provide a mobilecommunications which use a radio communications bandwidth and corenetwork resources as efficiently as possible, with respect to which MTCcommunications, for example, can provide a significant challenge.

SUMMARY OF THE INVENTION

According to the present invention there is provided an infrastructureequipment for forming part of a mobile radio network. The infrastructureequipment includes a transmit and receive unit, which is arranged inoperation to transmit and receive data to and from mobile communicationsdevices via a wireless access interface, and a controller for processingrequests for communications resources from the mobile communicationsdevices. A plurality of associated communications devices are arrangedto form a group, and each of the associated communications devices ofthe group includes the same common identifier, with respect to whichcommunications sessions can be established to communicate data via themobile radio network, and the controller is arranged in combination withthe transmit and receive unit to respond to a request from one of thecommunications devices of the group to establish a communications bearerusing the common identifier.

According to some embodiments each of the associated communicationsdevices of the group includes the same common identifier with respect towhich communication sessions can be established to communicate data viathe mobile radio network from any of the associated communicationsdevices. The group of communications devices may be for communicatingmachine type communications (MTC) for a particular application such asfor example, being disposed in a vehicle such as a car in order toreport certain parameters. Each of these parameters may be served by aseparate communications device which reports periodically on theparameters which are detected by an associated sensor. As such becauseof the spatial proximity of each of the communications devices, each isable to receive control plane signalling data and accordingly thecommunication of the signalling data is as if broadcast to a localenvironment in which the group of communications devices are disposed.Accordingly, there is a saving in communications bandwidth which isproportional to the number of the devices in the group.

The inventor of the present invention has recognised that a plurality ofcommunications devices maybe associated with each other, which can beefficient for example when communicating MTC communications. Forexample, a plurality of associated communications devices maybespatially disposed throughout a vehicle, such as a car, in order tomonitor parameters or events of interest such things as engineperformance, the temperature, the speed of the vehicle, direction oforientation and indeed the location of the vehicle. Each of theseparameters maybe served by a separate communications device whichreports periodically on the parameters which are detected by anassociated sensor. In another example the communications devices maybedisposed throughout a public transport vehicle such as a train or a busand may report on things like a number of passengers present in thevehicle, the amount of sales which have been made, the position of thevehicle and the performance of the engine. Other examples can beenvisaged in the application of embodiments of the invention.

Embodiments of the present invention provide each of the communicationsdevices in a group with the same identifier, for example by replicatingthe same Subscriber Identity Module (SIM) or for LTE the sameUniversal-SIM (U-SIM). As such although the communications devices maybe identified individually at, for example, the physical layer or theradio access layer of a mobile radio network, at a higher layer, forexample the media access control (MAC) layer or the application layer,the communications devices maybe addressed using a single identifier forestablishing a communications session or addressing. In one example theidentifier is an International Mobile Equipment Identity (IMEI). As suchall control plane data and signalling which is communicated to thecommunications devices of the group will be communicated as if themobile radio network is communicating with a single device. The controlplane or signalling data may be for example mobility managementsignalling within the evolved packet system. As such because of thespatial proximity of each of the communications devices, each is able toreceive the control plane signalling data and accordingly thecommunication of the signalling data is as if broadcast to a localenvironment in which the group of communications devices are disposed.Accordingly, there is a saving in communications bandwidth which isproportional to the number of the devices in the group.

In order to establish a communications session or switch thecommunications devices between an Evolved Packet System (EPS) ConnectionManagement (ECM) connected state and idle state, a first of thecommunications devices of the group is arranged in operation toestablish the communications session by transmitting signallinginformation including an identifier which is common to the group ofcommunications devices to the mobile radio network via one or more ofthe base stations. Each of the associated communications devices in thegroup is then arranged to receive signalling information communicatedfrom the mobile radio network on the downlink in response to signallinginformation transmitted by the first communications device on theuplink.

By arranging for one of the communications devices to transmit thesignalling information to establish a communications session, each ofthe associated communications devices within the group can transmit datato the mobile radio network and/or receive data from the mobile radionetwork using a communications bearer established by the firstcommunications device using the identifier which is common to all of theassociated communications devices of the group. Thus one of thecommunications devices of the group acts as a “master” to perform allNon Access Stratum (NAS) communications to the network whereas all ofthe associated communications devices of the group are arranged toreceive signalling information in accordance with NAS data from themobile radio network. Thus the associated group of devices is configuredsuch that one of those devices acts as a master for transmitting uplinksignalling data to the network and whilst the home subscriber server(HSS) may store data which identifies each of the communications devicesusing the International Mobile Equipment Identifier (IMEI), the MediaAccess Layer (MAC) layer will respond as if the communication in respectof signalling and control plane information came from a singlecommunications device. Accordingly, an efficiency in the communicationof control plane and signalling data can be realised.

In one example, in respect of authentication and registration of thegroup of associated communications devices, transmission of informationis done by the master device only.

In some embodiments the mobile radio network is arranged to communicatedata to and from the communications devices using a wireless accessinterface which includes a random access communications channel foruplink transmission of signalling data, and each of the communicationsdevices from the group of associated communications devices is allocateda predefined time among the group of devices to access the random accesscommunications channel. Accordingly since the communications devices areassociated with each other, between them they can be arranged to accessthe random access communications channel on a time divided basis to theeffect that contention for accessing the random access communicationschannel can be at least reduced.

In some examples the group of devices is sub-divided into sub-groups,each sub-group being allocated to one of the predefined times. In thisexample the allocation of the times to access the random access can bemade as short as possible, whilst still reducing an amount of contentionwhen accessing the random access channel. Therefore whilst in someexamples, each of the communications devices of the group could beallocated one time to access the radio access channel, this could resultin the devices having to wait too long to transmit a request for up-linkresources. Therefore, by sub-dividing the group of devices andallocating each of the sub-groups the same time to access the randomaccess channel, a balance can be made between the probability of somecontention access and a time which the communications devices have towait before accessing the random access channel.

In other embodiments each of the communications devices within the groupof associated communications devices is provided with one of a set ofsequences of data for use in identifying the communications device whentransmitting bursts of data to the mobile radio network via the wirelessaccess interface. Each of the data sequences may be used, for example,as a pre-amble, mid-amble or post-amble in a transmission foridentifying a source of the transmission when resolving contentionaccess. The group of data sequences is uniquely associated with thegroup of communications devices. Alternatively, the data sequence may bea spreading code. The mobile radio network may be arranged to determinewhich of the communications devices of the associated group transmitteda burst of data and in response grant access to uplink resources bytransmitting an indication of the grant of uplink resources on adownlink communications channel. To identify the device which is beinggranted the uplink resources, the data sequence which has been allocatedto that communications device is included in the signalling datagranting the uplink resources, which is transmitted on the downlink forexample as a pre-amble, mid-amble or post-amble or a spreading code.

Thus embodiments of the present invention provide an arrangement inwhich the group of associated communications devices is allocated apredefined sequence which might be for example used as a preamble fortransmitting data bursts via the physical layer for example the randomaccess communications channel. The mobile radio network can thenidentify which of the communication devices transmitted the data in therandom access channel. Accordingly, when granting uplink resources themobile radio network communicates a grant message which includes thesame preamble which it received in the request for uplink resources. Allof the communications devices are arranged to listen to the controlplane message allocating the uplink resources and using knowledge of theallocated predefined data sequence the communications device, whichrequested uplink resources, can identify itself as being granted thoseresources. Accordingly, for example, contention can be resolved betweenmobile communications devices which are allocated to the same sub-groupand which can transmit in the same random access channel.

According to some embodiments the master communications device isarranged to communicate all NAS communications for the group. However ifone of the slave communication devices of the group is communicatingwith the mobile radio network, when the network considers that ahandover to another base station should be made (network directedhandover) or the communications device itself considers that a handovershould be made (mobile directed handover), then that slave devicecommunicates the AS signalling data associated to execute the handoverfor the group. The other devices within the group listen for thedown-link and up-link AS communications so that they can receive anymessages required to attach to the target base station. If thecommunications devices of the group return to an idle mode then themaster device communicates all of the NAS signalling which is requiredfor mobility.

Further aspects and features of the present invention are defined in theappended claims and include a communications device for forming anassociated group of communications devices and a method of communicatingdata.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present invention will now be described withreference to the accompanying drawings in which like parts have the samedesignated references and in which:

FIG. 1 is a schematic block diagram of a mobile radio network and aplurality of user equipment forming a communication system whichoperates in accordance with the 3GPP Long Term Evolution (LTE) standard;

FIG. 2 is a schematic representation of a group of devices which iscommunicating with the wireless access network shown in FIG. 1;

FIG. 3 is a schematic representation of a car which includes a pluralityof communications devices which are reporting data generated by sensorsdisposed throughout the car;

FIG. 4 is a schematic block diagram of a bus which includes a pluralityof communications devices disposed throughout the bus which is reportingon information generated by sensors associated with each of thecommunications devices;

FIG. 5 is a schematic block diagram of three communications devicesforming and associated group;

FIG. 6 is a schematic representation of process through which a virtualmultiplexing is performed on the up-link between the group ofcommunications devices;

FIG. 7 is a flow diagram illustrating a process performed by a first ormaster communications device of a group and the other devices in thegroup in connecting to the mobile radio network;

FIG. 8 is a schematic representation of a physical layer channelsincluding a physical random access channel;

FIG. 9 is a schematic diagram illustrating the logical arrangement ofthe physical random access channel shown in FIG. 7 with respect tosub-groups of the communications devices;

FIG. 10 is a representation of a burst of data transmitted by thecommunications devices shown in FIG. 8;

FIG. 11 is a diagram illustrating a message exchange between one of themobile communications devices of a group with a base station in order togain access to uplink communications resources;

FIG. 12 is a flow diagram illustrating the operation of mastercommunications device when accessing the random access channel torequest uplink resources;

FIG. 13 is a diagram illustrating a message exchange between a first ormaster communications device of a group for non-contentious access touplink communications resources; and

FIG. 14 is a flow diagram illustrating the operation of mastercommunications device when accessing the random access channel torequest uplink resources.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments of the present invention will now be described withreference to an implementation which uses a mobile radio networkoperating in accordance with the 3GPP Long Term Evolution (LTE)standard. FIG. 1 provides the example architecture of an LTE network. Asshown in FIG. 1 and as with a conventional mobile radio network, mobilecommunications devices designated as user equipment (UE) 1 are arrangedto communicate data to and from base stations 2 which are referred to inLTE as enhanced NodeBs (eNodeB). As shown in FIG. 1 each of the mobilecommunications devices 1 includes a Universal Subscriber Identity Module(USIM) which includes information and parameters which allow the mobilecommunications devices to access the mobile radio network and to beauthenticated for services to which the users have subscribed.

The base stations or eNodeB's 2 are connected to a serving gateway S-GW6 which is arranged to perform routing and management of mobilecommunications services to the communications devices 1 as they roamthroughout the mobile radio network. In order to maintain mobilitymanagement and connectivity, a mobility management entity (MME) 8manages the enhanced packet service (EPS) connections with thecommunications devices 1 using subscriber information stored in a homesubscriber server (HSS) 10. Other core network components include thepolicy charging and resource function (PCRF) 12 a packet data gateway(P-GW) 14 which connects to an internet network 16 and finally to anexternal server 20. More information may be gathered for the LTEarchitecture from the book entitled “LTE for UMTS OFDN and SC-FDMA basedradio access”, Holma H. and Toskala A. page 25 ff.

Communications with a Group of UEs

Embodiments of the present invention provide an arrangement in which aplurality of communications devices maybe associated with each other andgrouped together in order to communicate data from different sources. Itis envisaged that these sources of data may include data generated bymachines so that the data maybe automatically generated sensor readingsor events which require logging or other data which is generated bymachines rather than by a human interaction. Embodiments of the presentinvention therefore find application with MTC communications. An exampleof the group of devices is illustrated in FIG. 2 where mobilecommunications devices 1 are associated with a group 22 and each iscapable of communicating with the wireless access network shown in 24.

Examples where it might be appropriate to group devices as shown in FIG.2 are provided in FIGS. 3 and 4. FIG. 3 provides an example of a carwhich includes a plurality of sensors A1, A2, A3, A4 which are receivingstimulus from other components within the car such as within the engine,monitoring the speed of the car or the tyre pressure etc. Any datagenerated by the sensors A1, A2, A3, A4 are fed to mobile communicationsdevices 32 which may be spatially disposed throughout the car 30.

Another example is shown in FIG. 4 which maybe a bus, for example a busproviding public transport. The bus may also include a plurality ofsensors B1, B2, B3, B4 and for example may also include a GPS device 45which generates information automatically to represent the location ofthe bus 40. As for the example shown in FIG. 3 each of the sensors B1,B2, B3, B4, 45 shown in FIG. 4 has an associated communications device46 for transmitting the data generated by these sensors B1, B2, B3, B4,45 to an applications program running on a server which is connected tothe internet. The data is communicated to that application program via amobile radio network.

For the examples shown in FIG. 3 and FIG. 4, since the plurality ofcommunications devices are commonly located, embodiments of the presentinvention aim to utilise that common location to reduce an amount ofsignalling over head which is required to establish a communicationssession and to communicate data from those communications devices viathe mobile radio network. Embodiments of the present invention havetherefore been devised to achieve such a utilisation and improvement inefficiency.

FIG. 5 provides a schematic illustration of three communications deviceswhich are adapted to form an associated group of devices which may forexample be used for the example applications illustrated in FIGS. 3 and4. Each of the three devices 50 shown in FIG. 5 includes a transmitterand receiver which are arranged to communicate data to and from a basestation of the mobile radio network 52. Each of the communicationsdevices includes a U-SIM module 54 and an application processor 56 whichis arranged to run an application program for communicating data to acorresponding application server connected to the mobile radio network.

As will be appreciated in some embodiments the application processor 56may be a very simple device or may not be included in the communicationsdevices 50, because the function provided by the communications device50 is only required to communicate data generated by the sensors via areceiving input 58.

According to embodiments of the present invention the U-SIM 54 for eachof the communications devices 50 contains the same identifier whichidentifies the communications devices to the network for the purpose ofestablishing a communications bearer. Thus the U-SIM may include theinternational mobile subscriber identity number (IMSI) or the GUTI whichis common for the group of communications devices. Thus as shown in thetable below the group of communications devices 50 shown in FIG. 5 canbe addressed using various identifiers depending on whether it is anAccess Stratum communication or a Non Access Stratum (NAS/AS)communication. For an AS communication the cellular radio networktemporary identifier (CRNTI) maybe used for establishing acommunications session for all members of the group. Also shown below isa table providing an indication of various ways in which the group orcluster of mobile communications devices may be addressed including howa higher layer identification maybe made using one unique URL/URI or IPaddress for the group or cluster.

Cluster identifiers Domain Identity AS One C-RNTI per group/cluster NASOne IMSI/GUTI per group/cluster One IMEI per device Higher Layer Oneunique identifier e.g. URL/URI etc. per device One IP address pergroup/cluster

The communications devices 50 shown in FIG. 5 may also include an uplinkreceiver 60 which is arranged to detect and recover data transmitted byother communications devices of the group on the uplink to the mobileradio network using the transceivers 52.

As will be appreciated from the following explanation in otherembodiments the uplink receiver 60 may be omitted.

As will be explained in the following paragraphs, in order to realise anefficiency gain by reducing the control plane signalling, one of thedevices of the group acts as a master device and performs thetransmission of signalling and information on the uplink to the mobileradio network to establish a communications session and to maintain acommunication session in accordance with an enhanced packet systemmobility and connection management ECM/EMM) function whereas the otherdevices of the group only listen to the down link communications. Thuspart of the improvement in utilisation and efficiency of reducingcommunications and control plane information is that only one of thedevices of the group is transmitting control plane information in theuplink.

FIG. 6 provides a system level organisation of the devices in the group.As illustrated by a box 70, as far as higher layer network functions areconcerned, such as the radio access layer, all of the communicationsdevices in the group can be regarded as a single communications device.Each of the devices in the group act as passive or “slave” device andone of the devices of the group acts as a master device. When none ofthe devices in the group are transmitting or receiving data then thecommunications devices enter an ECM Idle state 72. However, in respectof communicating either AS or NAS data any of the n communicationsdevices of the group can enter an ECM connected state 74, 76, 78 inwhich case one of the devices is transmitting on the up-link and theother communications devices are receiving. Thus all of thecommunications devices of the group can enter an ECM connected state,but only one of the devices can be granted up-link resources at a time.However all of the devices in the group enter the ECM connected state inorder that they can receive down-link transmissions as in effect a pointto multi-point communication. Generally, the master communicationsdevice transmits all up-link messages for establishing a communicationsbearer, which is associated with NAS communications.

In FIG. 6 provides a flow diagram which illustrates a process by whichthe master communications device establishes a communication session forthe group of associated communications devices shown in FIG. 5. The flowdiagram is summarised as follows:

S1: One of the communications devices of the group acts as a mastercommunications device or UE and establishes a communications session bycommunicating signalling information for example via the random accesschannel in order to perform the necessary communication with the mobileradio network. For example, the master UE may perfoim a PDP contextactivation request, or PDN connection request for establishingcommunications bearer or a similar bearer request protocol. The masterUE uses the IMSI/GUTI or other identifier which is common to all membersof the group. The master UE maybe for example the first UE of the groupwhich wishes to communicate data via the mobile radio network in whichcase it acts as the master UE for establishing communications session.The other UEs may detect the control plane data using the uplinkreceiver 60. Alternatively one of the group members of thecommunications devices of the group may be pre-designated as the masterUE and programmed accordingly in which case the uplink receiver 60 canbe omitted to form a more simplified architecture.

S2: The other communications devices of the group which are associatedtogether listen for the down link signalling information which isprovided in response to the uplink transmissions form the master UE. Thedown link signalling information will include data required for mobilitymanagement and all. Non Access Stratum (NAS) information.

S4: although not part of the communications sessions establishmentprocess, the master communications device continues to performauthentication and other NAS type communications for the group ofdevices. Correspondingly, all the devices in the group monitor the downlink communications for receiving the necessary information as if thecommunications device itself had performed the uplink communication.

S6: All other communications devices monitor and decode the controlplane signalling to detect when the group is moved from an ECM_IDLEstate to an ECM_CONNECTED state.

According to embodiments of the present invention, the followingadaptations are applied to a group of communications devices to functionas a group so that improvements in the efficiency in control plane/NAScommunications can be achieved:

-   -   The group/cluster is identified by a unique C-RNTI and GUTI/IMSI        common to all communications devices of the group.    -   Communications from the mobile radio network to the group on the        downlink appear as broadcast transmission with no adaptive        modulation and coding.    -   For downlink communications to the group of devices paging is        supported.    -   For uplink communications, a communications device must reserve        uplink resources for a uni-cast transmission.    -   Only the master communications device can be re-authenticated        and performs other NAS procedures.    -   Slave devices can implement a subset of procedures which are        mandatory for the master group device.        Identification of the Associated Communications Devices of the        Group

In some embodiments devices forming a group/cluster are indexed oridentifiable separately from each other. As indicated above for theexplanation of FIG. 6, this can be realised during the attachmentprocedure when the explicit authentication procedure is invoked(requesting IMEI) or implicitly when this information is managed bysubscription information (USIM data). In the former case a standardprocedure is used and C-RNTI per device is allocated during transitionto the ECM_CONNECTED state (reserved pre-ambles are used in the randomaccess (RA) procedure). After transition to ECM-IDLE, the followingapplies:

-   -   1. Devices foaming a group/cluster must be indexed. This can be        realised during attachment when the explicit authentication        procedure is invoked by the network. (the network requests IMEI        which uniquely indentifies the device in the cluster and the        index can be then allocated) or implicitly when this information        is managed by subscription information (the USIM data). In the        latter case, master device attaches to the network. In the        former case a standard attach procedure is used by all devices        in the cluster and one of them becomes the master device. After        the attach procedure is completed all devices make transition to        the ECM-IDLE state then the following applies.    -   2. After having all devices in the group registered the system        can page the whole group (devices are in        ECM_IDLE/EMM_REGISTERED).    -   3. One device in the group is marked as a master device (e.g.        the device which was first attached or has special capabilities        in the case when slave devices are simplified). This device        responds to the paging message and is also the anchor device for        NAS procedures i.e. re-authentication, the TAU procedure etc.    -   4. The device which wants to initiate the uplink transmission        uses its unique preamble to invoke the RA procedure (the message        1). Once its preamble is echoed in the message 2 and possible        contention is resolved in the message 4 the temporary-RNTI is        promoted as the group C-RNTI.    -   5. Other devices passively listen to the RA procedure messages        in order to obtain parameters such as the group C-RNTI. This is        accomplished by searching for the group NAS identity (in the        message 4) and optionally group pre-ambles (in the message 2)        The timing advance parameter might also be used however it might        not be accurate for dispersed devices. The TA correction will be        obtained later when the MTC device invokes the RA procedure)    -   6. To save power the MTC device in ECM_IDLE are allowed to        invoke the RA procedure at predefined time slots according to a        function e.g. f(device number/index, IMSI)=hyper/radio frame        number/sub frame/TTI etc. This is required to prevent slave        devices from constant monitoring of the PDCCH to obtain C-RNTI        (Conventional LTE devices can trigger the RA procedure at any        time other devices in the cluster must detect this in order to        obtain the group C-RNTI. This would be inefficient from a power        saving point of view to require all devices to monitor the PDCCH        constantly. This principle is similar to listening to the paging        occasions. As an alternative predefined rules can be used for        selecting the PRACH resources to be accessed by the group and        this information enabled the MTC devices to choose timing        occasions when the PDCCH needs to be monitored)    -   7. After the master device is triggered by the paging message,        other slave devices passively decode any DL transmission        constantly monitoring the PDCCH.    -   8. A sudo random function is defined: f_rand(hyper frame number,        device number/index, preamble group)=preamble index. The        function is used to make sure that all devices in the group use        a different preamble when the contention based RA procedure is        invoked. As the RA response message can be delayed, the function        can not assign the same preamble indexes for X frames/TTIs. This        is necessary to distinguish between two RA attempts from devices        belonging to the same group/cluster (a contention resolution        will not work for these devices as they have the same NAS        identifier). Please note that devices can clash in the group and        this is resolved by the use of unique preambles. Any contention        with UEs which do not belong to the group is resolved by means        of NAS identifiers.    -   9. Once the MTC device has been granted the UL resources, the        message 3 is sent (see Annex 1). After any contention has been        resolved (with devices which do not belong to the group/cluster)        the cluster device starts transmitting UL data.    -   10. Other devices in the group/cluster do not attempt to        initiate the UL transmission until there are not any allocations        on the PDCCH for the group C-RNTI (an inactivity timer must also        expire) or the transmitting device and cluster are moved to        ECM_IDLE. The former requires the L2 protocols to be kept in        sync (e.g. sequence numbers etc.), the latter requires passive        decoding of AS signalling to detect when the RRC connection        release message is sent. This approach blocks other devices as        long as the transmitting device has data to send. Alternatively        the transmitting device stops after e.g. Y TTIs/ms so that the        transmitting device is moved to ECM_IDLE allowing other devices        to request UL resources (via the RA access) and start        transmitting. This is effectively implicit (without signalling)        UL transmission brokering between cluster devices.    -   11. L2 synchronisation may be achieved explicitly by monitoring        or implicitly by resetting the L2 protocols to a default state        after there are not any allocations on the PDCCH for some        predefined time (i.e. the inactivity timer expires).    -   12. MTC devices can also be restricted in that how much data        they are allowed to transmit once they become the transmitting        device regardless if the L2 synchronisation or transition to the        ECM-IDLE state are used to indicate to other devices that they        are permitted to initiate the UL transmission.    -   13. Only master device can be re-authenticated and performs        other NAS procedures.    -   14. Slave devices can implement a subset of procedures which are        mandatory for the master group device.    -   15. Devices which join the group later may need to initiate the        attach procedure which will be handled by the MME differently to        the first attach i.e. the IMEI is always requested from the MTC        device, the device is authenticated and security functions are        triggered (new security credentials are passed for the whole        group). No new PDP context is established just the existing PDP        context information is passed.    -   16. The UL virtual multiplexing concept which uses random access        procedure (preamble and NAS contention resolutions) used for        data transfer to terminals belonging to the group is illustrated        in FIG. 6.        Up-Link Communication by Communications Device in the Group

As will be appreciated from the explanation provided above only themaster communications devices is arranged to transmit signallinginformation to establish a communications session. However any of thedevices iof the group may at some time transmit data in the up-link andtherefore wil require up-link resources. Conventionally this is arrangedby the mobile communications device transmitting a random access signalin a random access channel such as, for example, the PRACH of the LTEsystem. The base station receiving the random access signal includes anarrangement to resolve contention between two mobile communicationsdevice transmitting a random access signal in the same up-link PRACH.However according to the present technique the group of communicationsdevices are arranged to reduce a likelihood of contention by dividingthe communications devices of the group into sub-groups of devices andpre-allocating a time when the communications devices of the sub-groupcan access the PRACH. As explained above, each of the devices in thegroup or at least the sub-group is provided with a unique data sequenceto use as a pre-amble, mid-amble or post-amble, which can be used toresolve contention.

As explained above in some embodiments predefined sequences areallocated to the group of associated communications devices, which areunique to each of the communications devices in that group or at leastwithin a sub-group which are allocated the same times for allocating theup-link random access channel. Accordingly, in the event of acontentious access of the random access communications channel themobile radio network can respond by identifying if possible which of thecommunications devices successfully accessed the random accesscommunications channel. This arrangement is illustrated in FIGS. 8, 9and 10.

FIG. 8 provides an illustrative representation of the SC-FDMA uplinktransmission scheme for the physical layer which includes a plurality oftime slots which are divided from a 10 millisecond frame into slots of0.5 milliseconds. More detail is provided according to the LTE standardas explained in chapter 5 of “LTE for UMTS OFDMA and SC-FDMA based radioaccess” by Holma H and Toskala A at page 83 ff”. In addition, thefrequency band is divided so that a matrix arrangement provides the UE'sa plurality of communications physical channels which are allocated bythe mobile radio network to the UE's on request. The request for anallocation of uplink resources is provided by transmitting a signal in aphysical random access channel (PRACH). A logical arrangement of theaccess to the random access channel PRACH is shown in FIG. 9.

According to the present technique in order to avoid contention betweenthe communications devices of the group each device is allocated a timewhen it can, if it needs to, access the PRACH according to a function(f_rand) of the hyper frame number, the radio frame number, the devicenumber or its index (the cell phone number being the same for all of thecommunications devices of the group) and the TTI, which has beenexplained above. Thus each of the communications devices within thegroup is provided with a predefined time slot in order to access thePRACH. As shown in FIG. 9 each of two communications devices, UE1, UE3is allocated the same time 100 in a first sub-frame 102 when it cantransmit, if it needs to, a random access signal in a PRACH channel. Asecond sub-group of device UE2, UE4 is allocated a second time 104 in asubsequent frame 106 when either device can transmit a random accesssignal. By sub-dividing the devices of the group into sub-groups alikelihood of contention between the communications devices of the groupis reduced.

In order to balance a likelihood of their being contention on the PRACHand a time that each of the communications devices has to wait beforethey can request Up-link resources, more than one communications devicemay be allocated to the same PRACH. That is to say that the group ofdevices are divided into sub-groups and each of these groups isallocated the same PRACH, within a scheduled time sharing of access tothe PRACH. Therefore there is no limit on the size of the group withrespect to a minimum time for access a PRACH or a capacity of the PRACH.However, as a result contention access will occur. Accordinglycontention resolution is required. To this end, each of thecommunications devices of the group is provided with a unique datasequence which it uses as a preamble for transmitting in the PRACH. FIG.10 illustrates a burst of information which maybe transmitted in thePRACH and includes a preamble field 90 and a Non Access Stratum (NAS)identifier 92. Each of the communications devices is provided with aunique data sequence from one of 64 possible data sequences for use as apreamble. As illustrated in FIG. 10 each of the devices of the group isprovided with a unique preamble whereas other devices within the cellattached to the base station are provided with a different set ofpreamble sequences or another group of communications devices isprovided with a different set of preamble sequences from the 64available preambles.

Since each of the devices within the group is provided with a uniquepreamble, when one of the communications devices transmits a burst inthe PRACH then the mobile radio network is able to identify that theuplink resources are required by the particular communications device.Accordingly when granting uplink resources, the mobile radio network andmore particularly the base station/eNodeB perhaps in combination withthe S-GW or the MME responds with that communication device's uniquepreamble so that when listening to the grant of uplink resources, thatcommunications device is able to identify that communications resourcesfor the uplink have been granted to it.

A representation of the contentious access for uplink communicationsresources for the group of communications devices is provided by themessage flow shown in FIG. 11, is reproduced from TS 36.300 andpresented here is assist in understanding the embodiments of the presenttechnique. The message exchange illustrated in FIG. 11 provides fourmessages, which are explained as follows:

-   1) Random Access Preamble on RACH in Uplink:

A communications device of the group of communications devices uses apreamble which has been derived from the f_rand function. The preambleuniquely identifies the communications device within the group.Contention may still exist for access to the random access channel. Ifanother communications device from the same sub-group also transmitscontemporaneously in the random access channel then path loss may beused to determine which group a preamble is selected from. The group towhich a preamble belongs provides an indication of the size of themessage 3 and the radio conditions at the UE. The preamble groupinformation along with the necessary thresholds are broadcast on systeminformation.

-   2) Random Access Response Generated by the Media Access Layer (MAC)    on the Downlink Shared Channel (DL-SCH):

The communications devices identifies that the grant of uplink resourcesis for it using the unique random access preamble identifier.

This communication is semi-synchronous with message 1, because it iswithin a flexible window of which the size is one or more transmissiontime interval (TTI). There is no HARQ, the message is addressed to theRA-RNTI on the PDCCH. This message conveys at least the random accesspreamble identifier, Timing Alignment information, initial uplink grantand assignment of Temporary C-RNTI, which may or may not be madepeimanent upon Contention Resolution. This is intended for a variablenumber of UEs in one DL-SCH message.

-   3) First Scheduled Uplink Transmission on the Uplink Shared Channel:

This message is sent by the communications device which recognised itsunique preamble in message 2. The message has the followingcharacteristics:

-   -   This message uses Hybrid Automatic Repeat Request (H-ARQ);    -   The size of the transport blocks depends on the uplink grant        conveyed in step 2 and is at least 80 bits.    -   This message conveys the radio resource connection (RRC)        Connection Request generated by the RRC layer and transmitted        via CCCH;    -   This message conveys at least an NAS UE identifier but no NAS        message;    -   RLC TM: no segmentation;    -   For RRC Connection Re-establishment procedure (only by the        master communications device);    -   This message conveys the RRC Connection Re-establishment Request        generated by the RRC layer and transmitted via Common Control        Channel (CCCH);    -   RLC TM: no segmentation;    -   This message does not contain any NAS message.    -   This message is communicated after handover, from the base        station in the target cell, but only from the master        communications device;    -   This message conveys the ciphered and integrity protected RRC        Handover Confirm generated by the RRC layer and transmitted via        DCCH;    -   This message conveys the C-RNTI of the UE sending it as        established when requesting uplink resources or following a        Handover Command;    -   Includes an uplink Buffer Status Report when possible.    -   For other events this message is sent by the communications        device which recognised its random access preamble in the        message 2.

-   4) Contention Resolution on the Downlink:

All of the communications devices in the group listen to the message 4including the communications device which recognised its random accesspreamble identifier communicated in message 2. This message ischaracterised by the following attributes:

-   -   Early contention resolution is used in that the eNodeB does not        wait for an NAS reply before resolving contention;    -   This message is not synchronised with message 3;    -   This message uses Hybrid Automatic Repeat Request (H-ARQ);    -   This message is addressed to the Temporary C-RNTI on the PDCCH        for initial access and after radio link failure to the C-RNTI on        PDCCH for UE in RRC CONNECTED;    -   H-ARQ feedback is transmitted only by the UE which detects its        own UE preamble identifier, as provided in message 3, which is        provided in response to the Contention Resolution message;    -   For initial access and RRC Connection Re-establishment        procedure, no segmentation is used (RLC-TM);    -   The Temporary C-RNTI is promoted to C-RNTI for a UE which        detects random access success and does not already have a        C-RNTI; it is dropped by others. A UE which detects random        access success and already has a C-RNTI, resumes using its        C-RNTI.

In summary FIG. 12 provides a flow diagram indicating the operation ofthe group of communications devices when gaining access to the uplinkresources. The steps illustrated in FIG. 12 are summarised as follows:

S20: The communications device waits for its turn to transmit in theuplink PRACH in accordance with prearranged time division of theavailable PRACH timeslots in respect to the other communicationsdevices. The communications device uses its unique random accesspreamble to transmit a request to have uplink resources to the mobileradio network by transmitting a burst of signals using the preamble inthe PRACH. However this may be contemporaneous with anothercommunications device from the same sub-group or indeed anothercommunications device not within the group of associated communicationsdevices. This is because the random access procedure is used by thedevices which belong to the sub-group as well as devices which do notbelong to the group. There are two levels of contention, which areresolved by either using the preambles allocated by the device of thegroup and final resolution by an NAS identifier. The devices in thesub-group use preambles which are unique within the sub-group. The firstcontention resolution is used to discriminate between devices in thesub-group. If they are not in the sub-group, but belong to the group ofdevices, then contention should not occur because each sub-group isallocated a different time slot in order to avoid contention in thefirst place. However in both cases it is possible that devices which donot belong to the group of devices will attempt the up-link access andthis is the case when the second contention is resolved with the help ofNAS identifiers.

S22: If an eNodeB can resolve one of the random access transmission inthe PRACH, the eNodeB can respond by providing a response from the MACor downlink shared channel from the eNodeB and uses the random accesspreamble identifier of the communications device which transmitted inthe PRACH. Thus the eNodeB is able to uniquely identify thecommunications device from within the sub-group of to which it isgranting the uplink resources using the preamble assigned to thatcommunications device. Obviously if the random access transmission wasby a communications device which is outside the group then contention isresolved in the usual way as mentioned above.

S24: Having received a response from the eNodeB the communicationsdevice schedules its transmissions on the uplink in accordance with theallocated uplink resources provided there was no contention for theuplink PRACH when it transmitted its burst.

S26: If there was contention when the communications device transmittedthe random access transmission in step S20 on the PRACH, because anothercommunications device in the sub-group or a device outside the group ofdevices transmitted a random access transmission in the PRACH and theeNodeB cannot resolve the transmissions then the eNodeB will respondimmediately to indicate that there was contention on the random accesschannel. Thus the base station indicates that the request transmissionof the random access communication in the PRACH was unsuccessful.Accordingly the communications device identifies that its attempt togain uplink resources was unsuccessful and therefore re-transmits arandom access burst in the PRACH when its scheduled turn comes roundagain.

Non-Contention Access of Uplink Resources Used by Master UE

A non-contention based random access procedure is only used by thetransmitting communications device during handover or by the masterdevice when positioning data is requested. As with the othercommunications devices of the group, the master communications device isprovided with a preamble which is unique to that device. Furthermorerandom access is not contentious because the master communicationsdevice or the communications device responsible for effecting handoveris allocated a time to access the PRACH which is not shared with othercommunications devices. Accordingly there is no contention accessresolution required for the master communications devices, and so therequest for uplink resources explained above is modified for the mastercommunications device as explained below:

The three steps of the non-contention based random access procedure arerepresented by the message flow diagram of FIG. 13 and summarised asfollows:

-   0) Random Access Preamble Assignment Via Dedicated Signalling in DL:

The eNodeB assigns to UE a non-contention Random Access Preamble. Thisis a Random Access Preamble which is not within the set of pre-ambleswhich is sent to the other UEs from within the group for use inbroadcast signalling. This non-contention Random Access Preamble issignalled to the master UE using either;

-   -   A Handover command generated by target eNodeB and sent from the        source eNodeB for handover, which is handles by the master UE;        or    -   Using the PDCCH in the case of downlink data arrival or        positioning, which is again being handled by the master UE in        the group, although the other devices in the group also detect        the message;

-   1) Random Access Preamble on the RACH in uplink, which is    transmitted by the master communications device of the group. This    message is transmitted by the master UE using the non-contention    Random Access Preamble.

-   2) Random Access Response on the Downlink Shared Channel (DL-SCH):    This message is transmitted in a semi-synchronous manner to message    1 within a flexible window of which the size is two or more TTIs.    The message has the following attributes;    -   This message does not use Hybrid Automatic Repeat Request        (H-ARQ);    -   The message is addresses to RA-RNTI on PDCCH;    -   This message conveys at least timing alignment information and        initial uplink grant for handover, timing alignment information        for downlink data arrival; the random access-preamble        identifier.    -   This message is intended for one or multiple UEs in one downlink        shared (DL-SCH) message.

As illustrated in FIG. 14 the following steps are taken for the masterdevice to secure uplink resources:

S30: The master device receives a random access preamble for use inrequesting uplink resources from this serving base station.

S32: The master communications device transmits a request for uplinkresources using the non contentious random access preamble.

S34: The serving base station responds with the grant of uplinkresources on the down link shared channel.

As will be appreciated from the example embodiments described above,some or all of the embodiments can provide the following advantages:

-   -   A cluster of communications devices can be addressed by one        C-RNTI/IMSI. A cluster of communications devices can receive        data simultaneously via the downlink. Broadcast transmission        techniques are applied in a cell for localised delivery to a        cluster of communications devices The uni-cast paging procedure        is used to activate downlink reception in a cluster of devices.    -   In known systems the UE selects a preamble identifier at random.        According to some embodiments random access preambles are used        to discriminate between communications devices in a cluster.    -   Any device in the cluster can request uplink resources to send        data despite having the same NAS identifier (also C-RNTI). This        is enabled by defining an implicit brokering function which        prevents other devices to interfere by uncoordinated uplink        transmission. The E-UTRAN is not able to distinguish which        cluster device is transmitting.    -   A power saving means is defined for other communications devices        in the cluster of devices to limit PDCCH monitoring in ECM_IDLE.        Operation of the Associated Communications Devices

As may be understood from the explanation of the example embodimentspresented above, the following advantages are provided:

-   -   Authorisation and charging can be established for a        group/cluster of communications devices rather than for each        device individually;    -   NAS communications and procedures per group/cluster are handled        by a nominated master device providing a reduction in signalling        communications;    -   Implementation of the communications devices of the group apart        from the master device can be simplified (light weight slave        devices);    -   The group of communications devices can use one C-RNTI/IMSI;    -   Uplink data communications from the group of devices will be        aggregated across the group making communications for the        session more efficient.

In order to achieve these advantages it will be necessary for all of thecommunications devices of the group to monitor and decode control planesignalling, and hence the communications devices may include an up-linkreceiver 60. For example the communications devices of the group arearranged in one embodiment to detect when the group is moved to EMC_IDLE(no need for keeping Layer 2 in sync as the L2 is re-instantiated onre-transition to ECM_CONNECTED) and/or Layer 2 needs to be synchronisedin order to be able to initiate uplink transmission by other clusterdevices while in ECM_CONNECTED. This requires transmission monitoringfor the group C-RNTI. Furthermore adaptive modulation and coding cannotbe used for downlink communications, all devices in the group/clustermust have the same hardware capabilities including security functionsetc. In addition, in some embodiments, the following modifications aremade to the mobile radio network infrastructure:

-   -   A scheduling function at the eNodeB is modified in order to        enable “broadcast like” transmission for selected C-RNTIs;    -   The eNodeB must be pre-provisioned with information that a group        of communications devices form a cluster. The eNodeB marks the        allocated C-RNTI as the one used for group communication with        the cluster.    -   If the attach procedure is used by slave devices, the MME is        provided with an identification that subsequent attachments are        triggered by devices forming a group/cluster.    -   If connection oriented protocols at higher layers are used, some        restrictions and limitations might apply in the scenario when        one IP address is allocated to a cluster.

Various modifications can be made to the embodiments described abovewithout departing from the scope of the present invention as defined inthe appended claims. In particular although embodiments of the inventionhave been described with reference to an LTE mobile radio network, itwill be appreciated that the present invention can be applied to otherforms of network such as 3G, GSM, UMTS, CDMA2000 etc. The termcommunications device as used herein can be replaced with user equipment(UE), mobile communications device, mobile terminal etc. Furthermore,although the term base station has been used interchangeably with eNodeBit should be understood that there is no difference in functionalitybetween these network entities and that in other architectures the basestation will combine with radio network controller to perform some ofthe functions which have been performed by the eNodeB/Base Station inthe above description and therefore corresponding changes could be madewhen applying the above invention to GPRS, 3G or other architectures.

The invention claimed is:
 1. An infrastructure equipment for forming part of a mobile radio network, the infrastructure equipment including a transceiver configured to transmit and receive data to and from communications devices via a wireless access interface, and a controller configured to process requests for communications resources from the communications devices, wherein a plurality of associated communications devices are arranged to form each of plural groups, and each of the associated communications devices of a respective group includes the same common identifier, respond to a request from one of the communications devices of the respective group to establish a communications session using the common identifier, the communications session being used to communicate data to and from any of the communications devices of the respective group, provide each of the communications devices within each of the plural groups of associated communications devices with a unique one of a set of predefined sequences of data for use in forming a random access burst for transmission in a random access channel of the wireless access interface, a different set of predefined sequences being uniquely associated with each respective group, and transmit a message in response to a random access burst, using the predefined sequence which was used to form the random access burst received from a communications device.
 2. An infrastructure equipment as claimed in claim 1, wherein the common identifier, which is used to establish a communications session is provided using a subscriber identifier module or universal subscriber identity module, which includes the same common identifier for each of the communications devices in each respective group.
 3. An infrastructure equipment as claimed in claim 1, wherein the common identifier is a network temporary identifier or is used to generate a unique resource location or unique resource identifier.
 4. An infrastructure equipment as claimed in Claim 1, wherein the infrastructure equipment is arranged to identify each of the devices using an equipment identification number, the equipment identification number being used by a radio link layer to identify each of the communications devices within each respective group of communications devices.
 5. An infrastructure equipment as claimed in claim 1, wherein a first of the plurality of associated communications devices in a respective group is arranged to be a master communications device and the infrastructure equipment is configured to establish a communication session for the respective group in response to receiving signalling information including the common identifier from the master communications device, and transmit signalling information to the respective group of communications devices in response to the signalling information transmitted by the master communications device, such that each of the associated communications devices transmit data to the mobile radio network and receive data from the mobile radio network using the communications session established by the master communications device using the common identifier for all of the associated communications devices of the respective group.
 6. An infrastructure equipment as claimed in claim 5, wherein the signalling information transmitted in response to the master communications device includes information required for mobility management and connection.
 7. An infrastructure equipment as claimed in claim 1, wherein the communications devices forming each group are mounted on a common mobile system.
 8. An infrastructure equipment as claimed in claim 1, wherein the random access burst received from one of the communications devices includes data representing a request for uplink resources and in response to the transmitted random access burst the controller communicates a grant of uplink resources to the communications devices of the respective group, using the same predefined sequence allocated to the communications device and received in the random access burst.
 9. A method of communicating data from an infrastructure equipment forming part of a mobile radio network, the method comprising: providing a transceiver for transmitting and receiving data to and from communications devices via a wireless access interface, and processing requests for communications resources from the communications devices, wherein a plurality of associated communications devices are arranged to form each of plural groups, and the processing of the requests for communications resources includes responding to a request from one of the communications devices of a respective group to establish a communications session using a common identifier, establishing a communications session using the common identifier to communicate data via the mobile radio network to and from any of the communications devices of the respective group, providing each of the communications devices within each of the plural groups of associated communications devices with a unique one of a set of predefined sequences of data for use in forming a random access burst for transmission in a random access channel of the wireless access interface, a different set of predefined sequences being uniquely associated with each respective group, and transmitting a message in response to a random access burst, using the predefined sequence which was used to form the random access burst received from a communications device.
 10. A method as claimed in claim 9, comprising receiving the common identifier, which is used to establish a communications session, from a subscriber identifier module or universal subscriber identity module, which includes the same common identifier for each of the communications devices in a respective group.
 11. A method as claimed in claim 9, wherein the common identifier is a network temporary identifier or is used to generate a unique resource location or unique resource identifier.
 12. A method as claimed in claim 9, wherein the establishing a communications session for communicating data via the mobile radio network, using the common identifier includes establishing a communications session using a first of the plurality of associated communications devices which operates as a master communications device, and transmitting signalling information including the common identifier for each of the associated communications devices in the respective group when the respective group of communications devices are in a listening mode in which the signalling information can be received in response to the signalling information transmitted by a master communications device, such that each of the associated communications devices is configured to transmit data to the infrastructure equipment and receive data from the infrastructure equipment using the communications session established by the first communications device using the common identifier which is common for all of the associated communications devices of the respective group.
 13. A method as claimed in claim 12, wherein the signalling information received from the infrastructure equipment in response to the first communications device includes information required for mobility management and connection.
 14. A method as claimed in claim 9, wherein the infrastructure equipment provides a wireless access interface which includes a random access communications channel for uplink transmission of a burst of signals, and the method includes allocating to each of the communications devices from the respective group of associated communications devices a time for transmitting a random access burst in the random access communications channel in accordance with a predetermined arrangement.
 15. A method as claimed in claim 14, wherein the predetermined arrangement includes allocating a time to each of the communications devices of the respective group, such that one or more of the communications devices is configured to transmit the random access burst in the random access communications channel.
 16. A method as claimed in claim 9, wherein the random access burst includes data representing a request for uplink resources and the method includes in response to the transmitted random access burst, communicating from the infrastructure equipment to the respective group of communications devices a grant of uplink resources, using the same predefined sequence allocated to the communications device.
 17. A method as claimed in claim 9, wherein the communications devices forming each group are mounted on a common mobile system. 